1. Field of the Invention
The present invention relates to a process for the production of the dihydroperoxides of alkylbenzenes, and more particularly, to the production of diisopropylbenzene dihydroperoxide in good yield.
2. Description of the Prior Art
The hydroperoxidation of diisopropylbenzene (DIPB) with oxygen or air under aqueous, alkaline conditions is known to produce numerous products in addition to the commercially desirable dihydroperoxides (DHP). Methods to obtain DHP without the formation of large amounts of co-products have been the object of research since 1947.
British Patent No. 727,498 which issued in 1953 describes the continuous oxidation of DIPB and the monohydroperoxide (MHP) under aqueous conditions in the presence of sodium hydroxide (NaOH) or (Na.sub.2 CO.sub.3) until the MHP concentration is at least 45%. DHP is periodically or continuously extracted.
Another problem of the DIPB hydroperoxidation is the fact that it is also not easy to selectively produce DHP from (MHP). For example, when DIPB is oxidized in a batch reactor at 100.degree. C. for eight hours, according to known hydroperoxidation methods, a 62% conversion of DIPB is obtained. However, the oxidation product contains more MHP (45%) than DHP (18%). Improved accuracy in analysis of hydroperoxidation by-products has revealed that the DHP production reported in some old literature is actually DHP and the hydroxyhydroperoxides (HHP). The combined yield of MHP and DHP is 86.6%. (See, for example, Japan Kokai 78-68735). Although still further conversion leads to a decrease in MHP concentration and an increase in DHP concentration, the oxidation soon comes to a standstill (no more increase in peroxide concentration) before all MHP is converted to DHP and there is a considerable loss in oxidation selectivity. In other words, instead of converting DIPB to DHP, DIPB is converted to some by-products. Therefore, it is desirable to terminate the oxidation at the midpoint and to recover the unreacted feed material, DIPB and the intermediate product MHP, from the oxidation product solution, and to return them to the oxidation reactor after the resorcinol precursors (DHP and HHP) have been removed, instead of carrying out the oxidation until all DIPB is consumed. In such a continuous cyclic oxidation, the amount of DHP produced nearly equals the amount of DIPB consumed, and there is no net change in the concentrations of MHP in the feed and in the oxidation product. To meet this goal, assuming that the rate of DIPB oxidation to MHP equals the rate of MHP oxidation to DHP, one would tend to choose a feed containing about 1:1 ratio of DIPB and MHP for such a continuous cyclic oxidation. However, because of the presence of many side reactions which take place during the oxidation of a DIPB-MHP mixture, it is not always beneficial to keep the concentration of MHP near 50%. In fact, very good results have been obtained by keeping the concentration a little lower.
Sumitomo Chemical Company reported in Suda et al. U.S. Pat. No. 3,953,521 that m- and/or p-DHP are continuously produced by oxidizing the corresponding DIPB in liquid phase with air at 80.degree. C. to 130.degree. C., preferably 100.degree. C., in the presence of an alkali as catalyst, while keeping the concentration of MHP in the oxidation product solution in the range of 20 to 40% by weight. The level of by-product formation was not disclosed in this patent. It was shown in a comparative example that using the same reactor, about 120 parts of DHP were obtained from 100 parts of DIPB when the MHP concentration was kept at 38%, whereas only 70 parts of DHP were obtained from 100 parts of MHP when the MHP concentration was about 50%. Theoretically, 140 parts DHP are produced from 100 parts DIPB.
It is well recognized from many investigations that the DHP recovered by extraction of the DIPB oxidation product with an aqueous sodium hydroxide solution usually contains from 25 to 35 wt % HHP. The Sumitomo patent did not disclose any information on HHP concentration either in the hydroperoxidation feed or in the hydroperoxidation product.
According to Japanese Patent No. 53-68735, issued to Sumitomo Chemical Company, when a recycle hydroperoxidation mixture containing 45.8% DIPB and 39.1% MHP was oxidized with air at 100.degree. C. for five hours in the presence of 2% sodium hydroxide, a 71% yield to DHP and MHP was obtained.
This yield was 15% lower than the yield obtained when the oxidation was made with 100% DIPB under identical reaction conditions. No explanation was given for the lower yield. It suggests that in a cyclic hydroperoxidation process a lower yield of hydroperoxides can be expected. (See also Japan Kokai 58-88357).
Mitsui Petrochemical Industries' hydroperoxidation process is reported to be a noncyclic oxidation of DIPB. According to U.S. Pat. No. 4,237,319, a DHP-rich oxidation product was obtained by carrying out the oxidation of DIPB under alkaline conditions at a temperature in the range of 80.degree. C. to 110.degree. C., until the concentration of hydroperoxides at the end of the reaction reached at least 120 wt %, but less than 140 wt % (theoretical conversion of DIPB to DHP). The process coproduced a considerable amount of HHP and the dicarbinol (DCL) which must be converted to DHP in a separate reactor by an oxidation with hydrogen peroxide. Any unreacted DIPB and MHP were not recovered. Although the process eliminates the need to separate DHP by a caustic extraction followed by another extraction with an organic solvent, the values of DHP/DHP+HHP+DCL are calculated to be 71 to 73%. The mol % yield to DHP+HHP+DCL was reported in the range of 79 to 83%. It is estimated that the overall yield of Mitsui Petrochemical Industries' process for converting DIPB to DHP is not more than 75-80%. (See also Japan Kokai 61-180764).
A method of preparing diisopropylbenzene hydroperoxides under substantially anhydrous conditions in the presence of minute quantities of a barium oxide catalyst at temperatures between about 70.degree. C. and about 130.degree. C. is disclosed in Wu et al. U.S. Pat. No. 4,282,384.
A method for producing hydroquinone is known which includes the step of continuously oxidizing p-DIPB under nonalkaline conditions with oxygen or air at 83.degree.-87.degree. C. The mol % p-DIPB in the oxidate is 26%. Other products include DHP and MHP.
Additional hydroperoxidation methods are disclosed in Voges U.S. Pat. No. 4,271,321 and Miller U.S. Pat. No. 3,883,600.
An object of the present invention is to provide a method of oxidizing diisopropylbenzene with improved selectivity for the dihydroperoxide. A further object of the present invention is to improve the production of the m-isomer of diisopropylbenzene dihydroperoxide.